The protagonist of Man from Mundania is seventeen-year-old Princess Ivy, daughter of King Dor and Queen Irene, older sister to Prince Dolph.

Princess Ivy sets off with her younger brother's co-fiancees Nada Naga and Electra to retrieve the magic mirror that had been stolen by the evil machine Com-Pewter, in preparation for her quest to find Good Magician Humfrey.

Meanwhile, in Mundania, an average college boy named Grey Murphy runs a computer program that claims that it will help him meet women.

When Ivy arrives, disorientated to find herself in Mundania, Grey starts to fall for her despite her claims that she is a princess from a fantasy world called Xanth.

It emerges that Grey is the son of Evil Magician Murphy and Vadne, both banished from Xanth in the book Castle Roogna, although they had never revealed their origins to him.